The challenge of adapting The Dark Tower into a movie is the same one faced by its gunslinger hero: How do you prevent this pillar of worlds from collapsing under its own weight?

Not only do the filmmakers have to please longtime Stephen King fans while significantly reworking a beloved literary work, they also have to entice newcomers without losing them in the labyrinth.

If it works and the $60 million film is a hit, there are unlimited plans for sequels and even a companion TV series, exploring all the further dimensions of King’s books. If moviegoers and critics balk, then The Dark Tower franchise will be like one of those unfinished buildings, where only the foundation was laid before work was abandoned.

BEST LAID PLANS

Over the past decade, heavyweights such as J.J. Abrams and Ron Howard have tried to bring King’s epic to the screen, but for many studios it was too big, too intricate, and too weird. (Not to mention the budget — too costly.) After so many false starts, the mere existence of the movie, which Sony Pictures and production company MRC studios will release on Feb. 17, is simultaneously a dream come true for King’s readers and something that fills them with trepidation.

King himself gets it. “I feel more wrapped up in this one because the books took so long to write and the fan base is so dedicated,” he says in an interview from his office in Bangor, Maine. So instead of keeping the film at arm’s length, he has been offering suggestions from afar. “They sent me a number of different drafts and it came into focus, let’s put it that way,” he says. “I’m 100 percent behind it — which doesn’t mean it necessarily will work, just that it’s a good way to try and to get into these stories.”

Among King’s obsessive readers is The Dark Tower director and co-writer Nikolaj Arcel, a Danish filmmaker who says he learned English as a teen just so he could read King’s books in their native language. Some may see a sinister story. He sees a fable about doing the right thing, the selfless thing. Despite the Tower’s ominous name, it actually stands for something good.

“The Tower is a beacon of light in a world that’s cynical and dark and sometimes feels a little hopeless, and this is about the quest for that,” says Arcel, who’s best known for directing Oscar-nominated Danish film A Royal Affair, and for writing the script for the Swedish version of The Girl With the DragonTattoo. “This is the quest to save the hope and the light.”

Here’s a look at what this movie will utilize from King’s epic saga, and what it will be putting aside for those later installments, if the audience for The Dark Tower is as stratospheric as they hope.

COMPLICATED SHADOWS

First, the movie is sticking to the triangulation of the first novel, The Gunslinger, begun when King was just a college kid and published in 1982 (with a revision in 2003 to bring it into line with the latter mythology.) Those three points are Idris Elba’s Roland Deschain, the Gunslinger; Matthew McConaughey’s Walter, The Man in Black; and newcomer Tom Taylor’s Jake Chambers, a 15-year-old with psychic powers that could either save the Tower or help Walter destroy it.

Roland chases Walter, Walter chases Jake, and Jake chases Roland. “It’s completely circular, cogs and wheels,” says Arcel, sitting beside a candlelit altar to the Crimson King, the mad god who will be unleashed if the Tower falls. “Everything fits together. It has a great little power to it. It fits very well into the nature of the entire saga itself.”

This theme – that fate (or “Ka” in the language of the Tower) is a wheel that always comes around to the same place while rolling us inexorably forward matches perfectly with King’s novels. But the movie is also taking some major liberties with the story, albeit with the blessing of the Creator.

“All I can say is that Steve is our partner all the way through, so we don’t make a move without Stephen telling us, ‘That is The Dark Tower’ and when Stephen says, ‘It isn’t,’ which he has at times, we go, ‘Okay, let’s try something else,” says Akiva Goldsman, an Oscar-winner for A Beautiful Mind, who co-wrote the script.

King didn’t just sign off, he made his own modifications. “I took a pen and cut Roland’s dialogue to the bone,” the author says. “The less he says the better off, and why not? Idris Elba can act with his face. He’s terrific at it. He projects that sense of combined menace and security. [Roland] is the Western hero, the strong, silent type: ‘Yep,’ ‘Nope,’ and ‘Draw.’”

After that, King was ready to let the wheel roll. “All I said was, ‘Yeah, go ahead and go with it. This is an interesting way to attack the material.’”

We’ll get into non-spoiler, general descriptions of what came from each book tomorrow, but for now, Goldsman said he tried not to cherry-pick only the most memorable parts of the saga, but rather blend pieces that would support what he considers the overall theme: sacrifice, friendship, and accepting as parts of your life become past-tense.

“The Dark Tower is about how we carry around our past, which of our ghosts travel with us, and how do we attend to them,” he says. “The ghosts of history, the ghosts of the people we’ve lost in order to get to whatever our Tower is.”

TWO LOST COMPANIONS

Without doubt, the most significant story change is the absence of two major characters who, in the books, were pulled from our world to join Roland’s quest: the reformed heroin junkie Eddie, and the amputee with multiple personalities, Susannah.

Constant Readers who’ve been following the production have probably noticed that no one has been cast in those roles yet. The bad news: they won’t be. Although… an allusion to them may be in the cards.

The good news: if there’s a sequel, they are guaranteed. (Keep reaching for those Bends ‘o the Rainbow, Aaron Paul.)

Dear @StephenKing,How goes it my friend? So, about these Dark Tower rumors. What are your thoughts? Could you put in a good word for me?Ap

Those fancasting Susannah can keep up their campaigns, too. No decision will be made about the future of The Dark Tower franchise until it’s clear there’s an audience for the first movie, although the relatively low budget improves the likelihood of success. At that point, we may even get to see the friendly billybumbler creature known as Oy joining the quest.

Arcel says he knows fans will miss Eddie and Susannah — he does too. But they didn’t join the saga until the second book, 1987’s The Drawing of the Three, and he felt it was important to establish the Gunslinger’s solitude before establishing his “Ka-tet,” or fate-forged family.

“They’re certainly out there,” Arcel says. “I think the entire story deserves to be told and should be told. I would certainly be disappointed in myself or my collaborators if we didn’t bring them in. They’re such a huge part of the story.”

King also consulted on those two sitting this one out. “I’m fine with it,” he says. “I know exactly where Akiva always planned to bring them in and that’s cool with me.”

THE SECRET SEQUEL

For others still worried about fidelity to the source material, there’s another twist to consider.

By the end of the books, Roland has come into possession of an artifact known as the Horn of Eld, which (vaguespoiler warning) symbolizes a cosmic reset button. Every time Roland starts the quest over again, the journey changes in big and small ways. In the movie, he already has this tool (you can see it peeking out of his bag in the image above), which means the film is not so much an adaptation as a continuation.

“The hardcore fans of The Dark Tower series will know that this is actually a sequel to the books in a way,” Arcel says. “It has a lot of the same elements, a lot of the same characters, but it is a different journey.”

It’s a strange journey, for sure. One that’s not only venturing through a very, very long shadow, but adding to it as it goes.

Coming up Friday: Part IV of EW’s online coverage of The Dark Tower, with a gallery of new images from the film.

Also: Stephen King himself on the covert connections between this movie and his other tales.